Optional prayers are silent in daytime, but one may recite loudly in them at night.

The followers in a group prayer keep silent.

Attendees of the Friday Speech keep silent (except if the speaker recites the aayah that orders to praise Prophet Muhammad (may Allah raise his rank.))

If one misses the obligatory night prayer, and performs it the next day in a group, then the leader of the prayer recites loudly. However, if one is praying it alone then one must recite silently.

Forgetting Fatihah

The one who recited Quran, but forgot to recite the Faatihah in the first two subsets of an obligatory prayer, does not catch them up in the last to subsets. However, if one recited the Faatihah in the two first subsets and nothing more, then it is waajib (a duty) to catch up by reciting it again with another suurah in the two last subsets (loudly if it was supposed to have been recited aloud). One must prostrate for innatentiveness (sujuud al-sahw) in both cases above.

Obligatory and Waajib Reciting

The obligatory required reciting is fulfilled by a single aayah. This must be done in every subset in optional prayer, but at least in two in obligatory prayers.

It is a duty to read at least an additional suurah or a long aayah after the Fatihah (except in the 3rd and 4th subsets of the 5 obligatory daily prayers).

It is a sunnah to read the Fatihah in all subsets in obligatory prayers (but one does not add to it other reciting in the 3rd and 4th subsets).

The preferred amount to recite

The Quran is divided into 30 parts, the last three of these as a unit are called "The Divided One" because its divided into many suurahs.

It is a convention in the Fajr prayer and the Thuhr prayer to recite in the first two subsets between 40 and 50 aayah, or the longer suurahs of The Divided One. This is in addition to the Faatihah.

Other numbers have been related, and the way to make agreement between the sayings is to say that the leader recites with the hard-working 100 aayah, but with the lazy only 40, and with average people between 50 and 60. Others said that the criteria is to look at how busy people are, especially with regard to Thuhr prayer.

In the Asr prayer and the Eisha prayer, one should read middle length suurahs from The Divided One. For the Maghrib prayer one should recite shorter suurahs from The Divided One.

The first subset of the Fajr prayer should be made longer than the second one. This is to help people make the group prayer at a time when they are sleeping or drowsy.

The first two subsets of Thuhr prayer are equally deserving of recital length. The same is true for all the prayers except the Fajr prayer, as mentioned. It does not matter if the first or second subset is longer than the other one by two or three aayahs.

The traveler recites the Faatihah and any suurah, if he is in a hurry.